closure_drift MCP server

closure_drift

Does v1.4.2 mean one thing in your repository?

$ git clone -q https://github.com/psf/requests && cd requests
$ closure-drift --compare v2.16.0 v2.16.1
A  v2.16.0  (commit bcd0e170ac20)
   label    2.16.0
   closure  3d2886b87c2a7b94   17 file(s)
B  v2.16.1  (commit f687e9f3d8b0)
   label    2.16.0
   closure  696b71ed6023f563   18 file(s)
   changed    requests/__init__.py
   only in B  requests/packages.py

==============================================================
DIFFERS UNDER ONE LABEL: both declare 2.16.0, and the code differs
in 2 path(s). If both were published, that label names two things.

Check it without this tool: git show v2.16.1:requests/version.py says 2.16.0. closure_drift reads the git history, not a package index: it shows what the tags contain, not which commit a published package was built from.

A version is a string a human edits. When two releases share a version and differ in code, one address names two artefacts — and nothing notices, because the version is all that was recorded.

One command checks it. Read-only, one file, no dependencies, no network.

Run it

curl -sO https://raw.githubusercontent.com/luizfnsilva/closure_drift/v1.2.0/closure_drift.py
python3 closure_drift.py            # inside any git repository

That measures your repository. ./reproduce.sh is something else: it validates closure_drift itself (its test suites, a long run) and does not look at your repository.

or pipx run --spec git+https://github.com/luizfnsilva/closure_drift@v1.2.0 closure-drift. Needs Python 3.9+ and git. To see the three possible answers first: python3 examples/demo.py, or read docs/DEMOS.md.

Check before you tag

--would-tag answers: if I tag this commit now, does its version already name different code?

# GitHub Actions
- uses: actions/checkout@v4
  with: { fetch-depth: 0 }
- uses: luizfnsilva/closure_drift@v1.2.0

Push the workflow before the first tag: a tag pushed together with the workflow that should run on it may not start it (then run it by hand, with workflow_dispatch: in its on:). mode: measure concludes only from two distinct labels; on the first release it is inconclusive, exit 2, so gate with would-tag from the first tag.

# pre-commit, on git push
- repo: https://github.com/luizfnsilva/closure_drift
  rev: v1.2.0
  hooks: [{ id: closure-drift-would-tag }]

Other pipelines: docs/CI.md.

For AI agents

An agent that tags and publishes can ask the same question first, through a Model Context Protocol (MCP) server, standard library only, with a would_tag tool:

claude mcp add closure-drift -- uvx --from git+https://github.com/luizfnsilva/closure_drift closure-drift-mcp

Codex CLI, Gemini CLI, Cursor, VS Code, Windsurf, and a rule to paste into AGENTS.md, CLAUDE.md or .cursorrules: integrations/. The server makes the check available; the agent has to call it and respect the answer. The barrier is CI.

The answer

Exit 0 means clean and nothing else. No input we tried produces a traceback, and no failure exits 1.

they point to, or the tag itself when the version is derived from it

• label — the version your project declares at each tag: in its build files, in the module

• closure — SHA-256 over (path, git object id) of the files that determine your output

The report also says how many tags it could not compare.

Options

Shortened. The full README is on GitHub.